I have tried out roughly ~10 51/x/x sab builds since the patch and they have all been viable (besides the first day before the hotfix when they all sucked). If you are having troubles with sab it most likely has to do with your target selection, rotation and positioning rather than the build itself.

Just aim for the middle of thickest pack of players, drop 5 clatrops charges, detonate, toss as many bombs as possible, carpet bombing>>annihilation bomb until it goes black....rinse repeat. Sing jingle bells to the sound of the AOE DOT ticking. oh and drop some land mines when you can, they are always fun.